Proton-Conducting Polyoxometalates as Redox Electrolytes Synergistically Boosting the Performance of Self-Healing Solid-State Supercapacitors with Polyaniline

Abstract

Energy storage devices with high volumetric and gravimetric capacitance are in urgent demand due to the booming market of portable and wearable electronics. Using redox-active molecules as electrolytes is a strategy to improve the capacitance and energy density of solid-state supercapacitors (SCs). In this study, polyoxometalates (POMs) are applied as proton conductors and redox mediators in polyvinyl alcohol (PVA) electrolytes, which increase the capacitance of obtained SCs with polyaniline (PANI). H3PMo12O40-loaded PANI electrodes provide pseudocapacitance with an eight-electron Faraday reaction in a charge–discharge cycle. This has rarely been reported in SCs before. The largest capacitance of SCs with H3PMo12O40 and H3PW12O40 as electrolytes is 7.69 F/cm2 (3840 F/g) based on a single electrode at 0.5 mA/cm2. In addition, POM electrolytes exhibit excellent self-healing ability, which is attributed to the rich hydrogen-bonding network between POMs and PVA. This study demonstrates that the capacitance of solid-state SCs is improved by using molecular redox-active electrolytes and showcases the potential of applying this strategy to other energy storage devices in the future.